Laser-Induced Fluorescence Measurement on Helicon Plasma Sources

Abstract

Summary form only given. Two helicon sources have been developed for the space propulsion experiments with the different scales of geometries and magnetic field intensities. One is the K2H device, and the other is the SPEX (space propulsion experiment) in DiPS (diversified plasma simulator). Both machines generate the helicon plasmas by the m=1 antenna with 13.56 MHz RF frequencies and 3 kW of input power. For Ar ion diagnostics, the diode laser based LIE (laser-induced fluorescence) system is upgraded with the master laser (Littman-Melcalf) and MOPA (master oscillator power amplifier) from one diode laser system (external Littrow cavity) for larger mode-hop free tuning range and powers. Total tuning range is 140 GHz and the power up to 200 mW. Electric probes (single and Mach probes) are used for the measurement of plasma density, electron temperature, and ion flow speed/specific impulses. Using the LIE and electric probes, the plasma parameters in the two helicon sources are measured with different axial directions. Typical plasma densities, electron temperature, ion temperature, and flow velocities are >1013 cm-3, ~3-10 eV, <0.2 eV and <0.5Cs (Cs is the ion sound speed).